Document feeder with improved recyclable document control
The present invention is a continuation-in-part of U.S. application Ser. No. 172,978 filed March 28, 1988, which is a continuation of application Ser. No. 800,758 (now abandoned). 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to document copying devices and particularly to sheet-feeding mechanism for advancing, seriatim, the individual sheets from a stack of sheets to be copied. 
     The stack of sheets is placed on a holder, and the mechanism automatically feeds the bottom-most sheet onto the copier on demand, as the copier operates. 
     In the past, sheet-feeding mechanisms have generally been large, bulky, and heavy, supported to one side of the copying surface on or adjacent the frame of the copies, with complicated drive-mechanism to interact between the sheet-feeder and the copier when the sheet-to-be-copied is advanced to the copy position of the copier. 
     Illustrative of the type of document feeders known in the past is that shown in FIG. 12 wherein, as well as in my own U.S. Pat. No. 4,674,735 issued on June 23, 1987. See also British Patent 922,780 and U.S. Pat. No. 4,368,881. 
     SUMMARY OF THE PRESENT INVENTION 
     In the present invention, the document feeder is a compact, box-like unit which rests directly upon the glass plate copying surface of the copy machines. It can be used with copiers having a stationary copying surface or those having a reciprocating copying surface. It is to be understood that the copying machines, which may be well-known office copiers, facsimile, or electronic mail copiers, (as well as the copies which are made thereby), are not a part of this invention. 
     The document feeder has a cover which also functions as a tray-support for the documents to be copied. When the operator chooses to use the document feeder, the box is placed directly upon the glass plate of the copy machine and the cover is raised into an inclined support-position for the documents. 
     The set of document s to be copied is placed face-up on the inclined support with the first page on the top, and with the bottom (or last) page of the document, as it rests on the tray, coming into contact with a feed roller of the feeder. 
     Upon command, the feed roller rotates to remove the bottom sheet of the document from the tray support and (in cooperation with a drive-wheel) transfers it face-down onto the glass plate of the copier. 
     After the document has been copied, and while the copier is re-cycling, the drive wheel reverses direction, removes the document from the glass plate and transfers it face-up into a document-receiving tray. 
     During the next cycle, the drive wheel reverses and brings the next sheet from the stack of documents onto the glass plate, and the sequence is repeated. 
     After all the sheets have been copied, the documents may be removed from the receiving tray, the document support can be lowered to its position as a cover for the feeder, and the feeder may be removed from the copy machine. 
     The copier discharges the newly-made copy face-up into its copy-receiving tray and, therefore, the new set of copies are in order, when finished, with the top page on top. 
     Inasmuch as the newly-prepared copies, as well as the re-stacked set of copied documents are discharged from the copier face-up, all copies and documents are in proper sequence with the first page at the top of the stack and re-stacking is not required. 
     The document feeder of the present invention is light-weight, simple and uncomplicated and can be manufactured inexpensively and sold at a reasonable price. It can be used with a copier by an inexperienced operator and does not need a skilled service person for installation or operation. 
     The principle object of the present invention is to provide a document feeder which is small, compact, high-speed, easily transported, lightweight, and inexpensive. 
     A further object of the present invention is to provide a document feeder which can be used with any standard and well-known copy machine having either a stationary glass plate or a reciprocating glass plate. 
     Another object is to provide a low-cost feeder which can be easily connected to the copier so that the operation of the feeder may be automatically controlled from the control panel of the copier. 
     With the above and other objects in view, more information and a better understanding of the present invention may be achieved by reference to the following detailed description. 
     DETAILED DESCRIPTION 
     For the purpose of illustrating the invention, there is shown in the accompanying drawings a form thereof which is at present preferred, although it is to be understood that the several instrumentalities of which the invention consists can be variously arranged and organized and that the invention is not limited to the precise arrangements and organizations of the instrumentalities as herein shoWn and described. 
    
    
     In the drawings, wherein like reference characters indicate like parts: 
     FIG. 1 is a top perspective view of the document feeder of the present invention. 
     FIG. 2 is another top perspective view of the document feeder of the present invention with the document support tray in elevated position. 
     FIG. 3 is a schematic side elevational view of the document feeder showing the sheet-path through the feeder mechanism. 
     FIG. 4 is a plan view of the document feeder on a copier, showing a flange to cover the unused portion of the glass and to position the document feeder. 
     FIG. 5 is a schematic illustration of the sheet-advancing feed wheels. 
     FIG. 6 is a schematic illustration of the forces acting on the sheets. 
     FIG. 7 is a greatly enlarged diagram of the frictional forces acting upon the sheets. FIG. 8 is a schematic illustration of an alternate feed/sheet separator mechanism. FIG. 9 is a schematic drawing of the power-train or drive-mechanism of the present invention. 
     FIG. 10 is a side elevation of a section as shown generally at 10--10 of FIG. 9. 
     FIG. 11 is a fragmentary cross-section shown generally at 11--11 in FIG. 4. 
     FIG. 12 is an illustration of a prior-art feeder. 
     FIG. 13 is a vertical schematic drawing of one form of paper-stop. 
     FIG. 14 is a vertical schematic view of another form of paper-stop. 
     FIG. 15 is a vertical cross-sectional view of one form of drive-wheel taken along lines 15--15 of FIG. 9. 
     FIG. 16 is a cross-sectional view taken generally along line 16--16 of FIG. 15. 
     FIG. 17 is a fragmentary front elevational view of a light-weight pivot arm for a paper-stop. 
     FIG. 18 is a vertical sectional view taken generally along line 18--18 of FIG. 17. 
     FIG. 19 is a perspective view of a modified version of the document feeder of the present invention. 
     FIG. 20 is a fragmentary vertical cross-sectional veiw of the paper feeder rolls. 
     FIG. 21 is a fragmentary vertical cross-sectional veiw of another portion of the document feeder of the present invention. 
     FIG. 22 is a cross-sectional view of the paper feeder rolls. 
     FIG. 23 is an enlarged fragmentary sectional view of another portion of the paper feeder rolls. 
     FIG. 24 is a vertical sectional view of the rolls similar to that in FIG. 23. 
    
    
     In the present invention, a feeder 21 of generally box-like configuration has a body 22 and a top 23 (shown open at 23-a and closed at 23-b). The body 22 has a bottom 24 which is a generally rectangular frame having side portions 25 and an opening 26-a(FIG. 4 &amp; 11) 
     The bottom portion 24 is designed to be placed upon the glass plate of a copy machine, but supported above the copier glass to provide a thin space 26-a of appropriate size between glass and feeder for a document to be received therein. 
     The top 23 is pivoted at 23-c so that it can tilt to the position shown in FIGS. 2 and 3, and thus provide an inclined document-support 23-a for a stack of documents 28. 
     As many as twenty or more documents can be supported face-up on the tray 23-a and the bottom sheet 30 of the stack of documents 28 comes into contact with a feed roller 31, disposed along a generally central line of the stack of documents. This arrangement eliminates drive wheels and separators near the edges of the documents which, in many cases, may be damaged or wrinkled or otherwise rendered unsuitable for easy separation and feeding of the documents. 
     The preferred embodiment may be inter-connected with the copier in such a way that the required few watts of the low-voltage power and timing (logic) may be derived directly from the copier. Alternatively, the feeder of the present invention may have its own logic. Power may be supplied from a wall outlet mounted transformer, the copier, or rechargeable batteries. If desirable, the unit can be powered by a dry-cell battery arrangement which would provide the lowest cost of a non-interfaced design. 
     Additionally, the size of the trays and supports and guides may be appropriately chosen for U.S.-size paper, or for the international size (DIN-A4) used generally elsewhere around the world, or legal-size paper (81/2&#34;×13&#34; or 81/2&#34;×14&#34;). 
     Because the feeder can be easily removed from the copier, the copier can be used without the automatic document feeder of the present invention. 
     After the document feeder 21 of the present invention is placed upon the copier 102 in alignment with the registration edge 118, and the tray 23 is elevated to support-position 23-a, the stack 28 of sheets to be copied is placed upon the tray 23, face-up. The feeder 21 is resting on the copier glass 112 and positioned by flange 100. 
     When the copy machine is started, the document feeder is also actuated, either by its own power and logic (in synchronism with the copier) or as instructed by the power and logic of the copier if connected thereto. Then the feed wheel 31 is caused to rotate in the direction of the arrow 32, moving the bottom sheet 30 from the stack 28 around the periphery of the wheel 51 and onto the top of the glass plate 112 in the thin space 26-a until it reaches the stop or abutment 34. At this moment, the sheet is in position to be copied and the copying takes place. 
     The drive wheels on the main shaft 70 are a pair (or more) of wheels 44 and a center wheel 51. The wheel 51 is rubber so as to provide a strong pull on the paper when it is in the bite between the wheel 51 and the cooperating wheel 55. These wheels are relatively firm and the force between wheels 51 and 55 is high enough to pull the document 30 from the stack and overcome the drag of the feed/separation rollers 31 and 37. The wheels 44 are larger in diameter than wheel 51 and very soft, such as the foam rubber used in upholstery padding. The larger diameter allows the wheels 44 to touch the glass, while the wheel 51 does not. The wheels 44 move the paper, without skewing, on-to and off-of the glass and, as only a single sheet is being moved, the force can be low. Wheels 44 may be about 6&#34; apart. 
     After the copying is finished, the drive wheels 44 and 51 are caused to rotate in the opposite direction (as shown by the arrow 35) and the sheet which was on the copier glass is driven around the drive wheels 44 and 51 (in direction of arrow 46) and deposited in the receiving tray 36. 
     With a center feed and separator, a center set of pull-out rollers 51 and 55 is needed, and it is preferred to have them driven at a speed faster than the feed from roller 31, and to have a one-way clutch 43 on the feed roller shaft 74 so it will turn freely as the sheet is pulled through the drive. If there is a document in the bite of rollers 51 and 55, these rollers pull the tail of the document through the bite of rollers 31 and 37, causing rollers 31 and 37 to roll at a higher speed than if driven by the motor 120, (as allowed by the one-way clutch 38). 
     The feeder drive is reversed by the reversal of the power polarity to the motor 120. All of the system then goes in the reverse direction EXCEPT that beyond the one-way drive 43. These parts (shafts 74 and 72, rollers 31 and 37, gear-train 122, and the slip clutch 38) are driven directly by the motor 120 in the feed direction through the one-way drive, but not in the reverse direction. The reverse roller system is a Very good way to feed one and only one sheet even when the documents in the stack are of different weights and have different surface finishes. Many of the common feed systems do not work satisfactorily as a bottom feeder because of the weight and drag of the documents above the sheet to be fed. This drag also causes multi-feeds. 
     One or more separation rollers 37, as shown particularly in FIGS. 3, 6, 7, and 9 operate to insure that only the bottom-most sheet 30 in the stack 28 is fed into the copying position. 
     The principle is simple, elegant and has wide tolerance, as shown particularly in FIGS. 6 and 7. If one assumes likely values of 300 g. of force between the feed roller 31 and separation rollers 37, a coefficient of friction of 1.2 for rubber to paper, or rubber to rubber, and a coefficient of 0.3 for paper to paper, the drive force of the feed roller 31 on the bottom of the bottom sheet 30 is 300×1.2=360 g. If two sheets are in the bite of the rollers 31 and 37, the force between them is still 300 g., but as the friction coefficient is only 0.3, the friction force is only 300 g.×0.3=90 g. If the one-way clutch 38 is set to give a maximum force on the paper of any value from 90 g. to 359 g., the system will function. Assume that the clutch is set to slip at 200 g. force tangent to the surface of roller 37, the friction force of the paper and roller is 360 g., but the force on the paper is limited to 200 g. Therefore, when one document is being fed, the top roller 37 will roll on the paper and slip on the shaft 72. With two or more sheets, the sheet on the side of the drive wheel 31 is acted upon by a net drive of 360-90 g.=270 g., and the sheet(s) not in contact with the drive roller 31 are acted upon by a force of 90-200=-110 g. (the negative sign shows that the force is in the reverse direction, i.e., up and to the right) as shown in FIGS. 6 and 7 and the upper sheet(s) move back out of the bite. With one sheet in the bite, the net drive is 360 g.-200 g.=160 g. and the sheet is driven forward. With no paper in the bite, the feed roller 31 drives the retard roller 37 in the direction of arrow 61. 
     Other feed/separation systems which may be used are a high coefficient of friction feed roller 39 with a moderate coefficient retard member 62 as shown in FIG. 5, or the wheel-and-fence system shown in FIG. 8. Here the extra sheets are not pushed back, but they are kept from feeding forward. 
     Other well-known feed/separator systems could also be used, such as a sticky-tape system marketed by the 3M Company. 
     The sheet 30 is slid onto the glass 112 with the two spaced guide rollers 44 to prevent skewing. The drive should be light enough to move the paper until it hits the end stop 34. The rollers can slip on the paper if the normal force is low, or a weak drive may be used, such as weak motor or another slip clutch. 
     A gate 45 is placed in the path so that when the sheet is returned by the reversal of the rollers 44 and 51, the paper is directed to the stacking tray 36 in direction of arrow 46. 
     A photocell and light 48 indicates when there is a sheet in position at the stops 34. 
     The photocell 48 may be a mechanical switch so that the light of the copier does not affect it. It may not be needed because the motor 120 can be driven long enough to be certain that the paper is at the stop 34. But it is preferred to have such a signal so that the logic knows that the paper is at the stop readied to be copied. The switch can also be used to indicate when the last sheet had been fed. The logic would be arranged so that when there is no signal two seconds after a FEED, a &#34;beep&#34; is sounded, and a light is illuminated to advise the operator to pick up the documents and/or to stop the copier. 
     With one drive motor 120 powering all the automatic document feeder on the in-feed, there is a need to stop the feeding after the sheet has reached the registration stop 34, and before the next sheet has reached the gate area 45. If the feed motion is-stopped too soon, the first sheet will not be registered on the glass; if too late, the lead edge of the second sheet will hit the first sheet as it exits, or it will have pushed down the gate so that the exiting of the first sheet is not diverted into the stacking area 46. Either way there will be a jam. 
     To solve these problems, the surface speed of the main drive rollers 55 and 44 must be much faster than the surface speed of the feed roller 31. Furthermore, the switch 48 detects the lead edge of the sheet as it is near the end of its path which is the registration end stop 34. 
     The preferred design has a thin steel stripper 49 resting on the glass 112 to strip the sheet from the glass when the rollers 44 and 51 rotate in direction of the arrow 35. The edge of the stripper 49 on the glass 112 must be sharp so the edge of the paper does not stub against it. The sharp edge may be guarded when the tray 23 is folded or when the entire feeder 21 is lifted from the glass of the copier 102. 
     The logic of the feeder can either be in the copier when the feeder and copier are connected, or in the feeder where there is no electrical interface. In the case where the feeder has all the logic there may be a photocell 136 near the center of the bottom 24, or at an edge or corner, to detect the motion of the copier scan lamp. The photocell 136 will then note the passage of the light from the copier scan lamp, and soon after the light passes the center of the feeder, the copying is completed, and it is time to remove one sheet from the glass and put on the next sheet. Some copiers keep the lamp &#34;ON&#34; for the backstroke, some do not. With the lamp &#34;ON&#34; on the backstroke, the feeder would be set to respond to every other light signal. 
     For some uses, it will be desirable to keep the sheet on the glass while several copies are made. Thus, if four copies of a three-page document are needed, the three-page document 28 is placed face-up in the tray 23-a and, with an interfaced unit, the copier would be set for &#34;4 copies&#34; and the &#34;Print&#34; button pushed. This would cause the interfaced feeder to feed the last document from the stack onto the glass. The copier would then make the four copies and on the backstroke between the fourth and fifth copies, the sheet would be removed and the next sheet put on the glass. Thereafter, the four copies are made, the documents are changed, and more copies are made. At the end, the top sheet is removed from the glass and placed in the stacking area 36, face-up, and on top. 
     The outer main drive rollers 44 are made of a very soft material so that their interference with the glass causes only the light force needed to move the paper but not so much as to cause excessive drag. The center roller 51 is of a smaller diameter so it does not touch the glass. The difference in diameter may cause paper stress as the paper curves around the curved path defined by 121. 
     In the improved design shown in FIG. 15, the shaft 220 is driven by a spline 221 which matches and fits the internal spline 222 of the hub 223 secured to shaft 70 by set screw 224. The left end of shaft 220 is free to move vertically but not horizontally as confined by fixed guides 225 of bearing plate 226 mounted on side frame 53. Also extending from 226 are ribs 227 which limit the axial motion of shaft 220. 
     Rollers 44 and roller 51 can be the same diameter, and rollers 44 rest on the paper, or the glass 112 if there is no paper there. The force is light, as determined by the weight of the part, and/or a spring load. There is a gap between the bottom of roller 51 and the paper or glass. The roller rubber tires 44 may be solid, strong material as the load on the paper is not determined by the deflection on the material. 
     The action of the feeder of the present invention may be better understood by the following description: 
     During the FEED operation, as the bottom sheet 30 of the set of documents 28 is separated and fed to the glass 112, the motor 120 through gears 122 drives the system in the direction of the arrows 32, 61 and 50 on rollers 31, 37 and 51, respectively. Roller 55 is driven by roller 51 and always rolls with it. Sheet 30 is moved to the lower left in FIG. 3 as the friction of roller 31 on the sheet 30 is higher than the slip-clutch setting of the retard roller 37. When the lead edge of sheet 30 hits the top side of gate 45, it pushes it down and moves into the bite of the rollers 51/55. These are turning at a higher surface speed than the sheet as rollers are turning at a higher surface speed than the sheet as driven by wheel 31, and have a greater pulling force. They thus pull the sheet out of the rollers 31/37 causing roller 31 to turn faster than it would have been driven. The document is curved around by guides 121 and stripper 49 onto the copier glass 112. It passes under the rollers 44 which are in light contact with the glass near the edges of the sheet. They move the sheet through the thin space 26-a between the glass 112 and the bottom plate 24 of the feeder 21 until the leading edge of the sheet hits the end stop 34. The rollers 44 have such a light drive on the sheet that they slip until the motor stops, as signaled by the electric-eye switch 48. The document is now positioned on the copier glass and the copies can be made. 
     During the TAKE-OFF operation, the motor 120 reverses and the shaft 70 drives rollers 44 and 51 in the direction of arrow 35 in FIG. 3. Since the rollers 44 are in contact with the sheet, the sheet is driven to the left in FIG. 3 and diverted by the sharp edge of stripper 49 into the bite of rollers 51/55. As the gate is normally in the position shown in FIG. 3, the sheet is guided in direction of arrow 46 into the stacking tray 36. 
     A feeder of the type described will feed one sheet and, as the end of that sheet exits the feed/separation rollers 31/37, the next sheet will start to feed. The sheets would be touching head to tail, but in the present invention, when the first sheet reaches the main drive rollers, it is pulled faster than it was fed. This faster down-stream feed will create a gap between the tail of the first sheet and the lead edge of the next. This gap will be larger if the main drive pull overcomes the drag of the feed roller. The one-way clutch 38 on the drive -shaft 72 allows it to drive, but as the first sheet is pulled faster than the drive, the drive roller 31 is free to turn faster. The gap between the tail of the first sheet and the lead edge of the next sheet, and thus the speed difference, must be enough that the first sheet is moved to the registration stop 34 before the next sheet, which starts to feed when the tail of the first is pulled from the feed rollers, reaches the gate area. 
     More than the theoretical gap must be allowed as the motor coast will move the lead edge of the second sheet. Also, allowance must be made for possible imperfect separation where the second speed is pulled into the feed/separation bite 31/37. 
     For some copiers, it will be preferred to have a long spring stripper 49 so that it extends under the left edge of a sheet 30 when on the glass 112. Thus the stripping of the sheet from the glass is not needed, because the left end was not resting on the glass. This will be best on copiers which do not copy that edge of the document, and thus the end of stripper 49 will not be seen on the copy. 
     When there is already a sheet on the glass, the TAKE-OFF operation precedes the FEED operation. 
     As shown in FIG. 9, the motor 120 drives a belt 123. This belt drives shafts 70 and 74 in the FEED direction. Due to the pulley and roller sizes, the surface speeds of the rollers 44 and 51 are much greater than that of the roller 31. When the motor is reversed, only shaft 70 is driven directly by the motor due to the one-way clutch 43 on shaft 72. 
     While a reflective photoswitch can be used for the paper switch 48, this requires electronics and could be confused by the bright light of the copier. A mechanical switch is preferred. 
     The novel design is for a very light force paper switch which rests on the glass. This requires a flag having a close tolerance as the paper is thin and weak and may be very close to the glass. The freedom of the flag to rest on the glass under the effect of gravity and/or spring pressure, in spite of mechanical tolerance of the parts or their warpage, is novel. 
     Two embodiments of the switch are shown in FIG. 13 and FIG. 14. The standard snap switch 201 is operated by the pivoted metal flag 203 which is pivoted on shaft 205 which is welded to the flag and is free to move vertically in slots 207 in the fixed holder 209. It is shown in its home position at 203 and in its deflected position as 204. The sketch also shows the bevel 208 on the bottom of the flag so that a sheet of paper does not get under the flag. This design assures that the sharp edge of the flag is lightly on the glass, but free to move in response to the edge of the paper. The flag is returned to its normal position by the spring of the switch. 
     As the paper hits the flag with a considerable velocity and as the flag needs to move with the paper and along the glass, there is sometimes a tendency for the flag to hop up and for the paper to slide under. This mode of failure can be eliminated by a light spring force downward on the flag, shown as springs 206. 
     FIG. 14 shows an alternate design which can be used where added headroom is available. The spring of the switch both returns the flag and adds the downward spring force needed on the flag. 
     FIGS. 17 and 18 show another design wherein the feet 210 and 211 of the flag 212 are pivoted at 213 so that the bottom of the feet always slide the glass plate and prevent the sheet from slipping beneath the flag. 
     FIG. 10 illustrates the gears connecting shafts 74 and The shaft 72 turns slower than shaft 74, as shown by the gear train 124. This saves power and permits use of a smaller motor. A belt can also be used. The shafts 72 and 74 are driven in the same direction as shown by arrows 50. Roller 37 is loaded against roller 31 with a known and constant force. This can be caused by a built-in interference of the rollers, depending on the softness of the rollers, or the bending of the shafts, to determine the force. The ends of shaft 72 may be guided in slots 52 in frame 53 (as shown in FIGS. 5 and 9) and loaded with a light spring (not shown) in direction of arrow 54. 
     FIG. 4 and 11 shows the feeder 21 on a copier 102 with a control panel 104, a cover 110, and a registration edge 108 and 118 around glass 112. The feeder 21 is positioned to insure that the document, when on the glass 112 and at the stops 34, is where the copier needs the document to be located for a proper copy to be made. A flange 100 fits between the lower edges of the feeder 21 and the edge 108 to hold the feeder in place, to block the light, and to provide a white surface on the copier glass. 
     EXAMPLE 
     In the present invention, the lead edge of the first sheet moves about 2&#34; from the feed/separator rollers 31/37 and is then gripped by the pinch of the main shaft roller 51 and its idler roller 55. The main roller pulls the sheet from the feed/separator bite, aided by the one-way clutch 38. With the customary 11&#34; long paper, the main roller must move the lead edge of the paper about 13&#34; to reach the registration stop; i.e., the 11&#34; length and an added 2&#34; around the main drive roller which gets the tail of the sheet on the glass. This motion must be done as the next sheet, which is being fed by the feed/separator rollers, moves toward the gate area. The next sheet can move about 3/4&#34; before there is any interference. 
     Thus, using the above figures, the limiting case for the minimum excess speed of the main drive over the feed drive is that the main drive must move the paper 13&#34; before the lead edge of the next sheet moves 3/4&#34; past the feed roller. The feed roller will not start to feed the second sheet until the tail of the first sheet has been pulled free of the roller, assuming the separation is perfect. Thus the main drive must move the first sheet the 2&#34; to the registration edge before the second sheet moves the 3/4&#34; to the gate area. The main drive must be over 2.7 times as fast as the feed. (Ratio=2/.75=2.6666 . . .) 
     In this embodiment with 0.75&#34; diameter feed roller, a 1.4&#34; diameter main drive roller, and a belt drive with a speed ratio of 3.33 faster main drive to feed drive, the main drive ratio is 6.2: i.e., comfortably over the minimum and allowing for motor coast and the occasional imperfect separation where the next sheet may be dragged by the first. The advance of the second sheet past the feed roller is about 0.6&#34; with a quick-stop circuit on the motor. (As a check, the calculated motion with a 6.2 ratio is 2/6.2=0.32&#34;. The paper feed speed, before the main drive pulls the sheet, is about 6&#34; per second at the normal 36 v. This suggests a delay of the quick-stop relay and the stopping of the motor of 46 ms, a reasonable number.) 
     To make several copies of a set of documents, it is desirable to automatically make a copy of each sheet in the set, and then recirculate the set of documents to do it again. 
     The revised paper path of FIG. 20 shows that the paper is fed onto the glass from the top tray (50) as now done. The Gate is in a new position (52) and the paper return path (54) is now above the top tray. Thus if a set of documents is stacked in the tray and a sheet (the bottom sheet of the face-up set, thus the last sheet of the set) is fed onto the glass, the copies is run, a photocell in the Autoloader sees the copies light, the sheet is taken off the glass and diverted into the top of the top tray. As the copier continues to run, the sheet are fed from the bottom of the stack and restacked on the top of the stack. 
     Thus is 3 copies of a 10 sheet set of documents were to be run, the set would be stacked in the top tray, the copier set to 30. Three collated copies would be made fully automatically. The set of documents would have been fed three times, and would end-up in-order in the top tray just where they started. 
     Referring to FIG. 19, a display and means to set a given number adds to the usefulness of the Autoloader. Also, it is useful to be able to set the Autoloader as it is made today, to make several copies in the &#34;Yellow-Button&#34; mode. Thus if 20 copies are needed of 3 pages, the Autoloader with a control panel and suitable logic could keep each sheet on the glass until it sees the copies light for 20 times, then change sheets. The copies would be set for 60 (20×3) in the example and would be running at full speed without interruption. 
     Often one comes to the copes with several sheets that are not a set. Thus one may want 3 copes of one sheet, 10 of another, and 40 of the third. These could be entered into my control panel which, in this case, could tell one to set the copier at 53 and run the job without the need for the operator to be there to make the settings and handle the paper. 
     Once I have a display and setting keys (levers or up/down buttons, etc.) I can give the Autoloader other features. With a 20 or 40 character display, I can provide the operator with prompts of what is to be done. These can be a short fixed phrase or a longer sentence that is scrolled. 
     One of the prompts can be the multiplication of the number of sets wanted times the number of sheets. I could tell the operator how to set a sorter to work with the system. I can remind the operator that more copies are needed to complete the job, even when the copier stops because its setting dial was too limited, the copier ran out of paper, or it jammed. 
     Referring to FIG. 23, with the example given above, it is easy for the operator to calculate that the copier was to be set for 30, as this is the product of 3 times 10. It is much more difficult if 14 copies are wanted of a 23 page report. The proper setting of the copier, 322 (the product of 14 times 23), needs time and effort to calculate. 
     Also, the operator must count the sheets of the input set of documents. These problems are solved here. 
     The preferred method of controlling this job is to have my unit detect when the top page of the set has been fed the first time. This is difficult as there will be sheet on top of it when it is fed. Thus the Autoloader logic can count the sheets in the set. It has been set to make 14 copies of the set of documents, it can stop when this has been done and signal the operator and/or turn off the copier. (This requires the display panel). 
     As shown in FIG. 23, the light arm (60) is raised to put the set of documents (64) in the top tray. it rests lightly on the top sheet until this sheet is fed, at which point it falls into a photoswitch (62) and stays there for the remainder of the run. The logic thus has information as to the number of sheets in the document set. 
     The switch is near the back end of the input tray so that the returning sheet (66) does not hit the switch arm. 
     (In many cases this calculated number will exceed the copier&#39;s dial setting, typically 19 to 99) and will require a user to restart the copies a number of times. The logic of the display should alert the user that the job is not done and the copier must be restarted. 
     Referring to FIGS. 2, 21, 22 and 24, reliable feeding/separation is very important to the Autoloader. It must perform this vital function in spite of aging of the rubber rollers, wear, and with many types of papers, The active-separation system used in a very good choice for this demanding application. It is so good that the feeder is factory set and NO operator adjustment is provided. 
     This has some drawbacks that can be solved if the operator is allowed to set it a bit more toward more-feed or toward more-separation in known steps. A blind setting such as the turning of a screw is to be avoided as it is too apt to be badly miss-set. 
     An understanding of the feed/separation system is needed. In any feeder, the difficult job is to feed ONE sheet every time. With too much FEED and not enough SEPARATION, one gets doubles or worse. The opposite direction is apt not to feed anything. A good feeder has a wide range of proper feeding between these problems at the extreme of the feeding range. 
     On the Autoloader, the FEED and SEPARATION roller material are the same, both are the best, longest-lasting, highest friction coefficient material I can get. The FEED roller turns in the direction of feeding all the time, but has an over-ride clutch so that paper can be pulled out of the bite by the faster moving main rollers. The shaft of the SEPARATION (RETARD) roller is turning in the opposite direction to that which would cause feeding and is connected to the roller by a spring loaded slip clutch. The normal force between the rollers is factory set by a spring (or weight). The clutch setting is factory set so that the torque of the clutch, as seen as a tangential force at the surface of the roller, is MORE than the force needed to slip one sheet of paper over another with the normal force provided. It is set to be LESS than the force that the rubber roller can drive a piece of paper. 
     Some typical numbers will help in understanding the wide tolerance of this type of system. The coefficient of friction of rubber-to-paper is in the range of 1 to 2. That between paper-and-paper and paper-to-glass is in the range of 0.1 to 0.4. (The coefficient of friction is the ratio of the force to cause slipping divided by the normal force. Thus with a 100 gram normal force the friction between two sheets of paper might be 30 grams, for a coefficient of 0.3.) 
     Using the above numbers, the slip clutch could be set anywhere from 40 to 100 grams--a wide range. The factory setting is in the area of 60. Thus even is the coefficients are different than expected, the feeder will work. Going through the math will show that it is the ratio of the clutch torque to the normal force that is critical. Thus either can be used to set the feed/separation. 
     FIG. 21 shows a simple way to change the normal force by one notch more or less. Spring 112 pulls the end of shaft 11A4 down to set the normal force. By changing the fixed end of the spring to a higher or lower hole, the force that the spring exerts on the end of the shaft is changed by a known amount. 
     Thus we have shown a way to change the normal force between the rollers by a set amount and thus change the feed/ separation ratio by a known amount. 
     FIG. 22 is the view of the separation system used today. The right end of the shaft pivots in the bearing 11A13 and the left end is guided with a roller 9118) in a slot in the bearing plate. It is important to reduce the friction in the system so that the forces are consistent. 
     FIG. 24 is a new way to make the spring-set slip clutch with five settings marked A-E. The collars 11A5 are set-screwed to the shaft 11A12. The bearings (11A6) are of Teflon for consistent low friction. Both the bushing 11A11 and 11B1 are keyed to the groove in shaft 11A12 so that they are free to slip on the shaft but not turn. The spring 11A10 sets the force of bushing 11A11 against the parts that hold the rubber roller 11Ab. The adjustment 11B3 can be turned so its finger is in notch the selected setting. (Preferably there is another finger and set of notches on the other side to keep the forces balanced). 
     Thus I have shown a way to change the slip clutch setting by a set amount and thus change the feed/separation ratio by a known amount. 
     It is to be understood that the present invention may be embodied in other specific forms without departing from the spirit or special attributes hereof, and it is therefore desired that the present embodiments be considered in all respects as illustrative, and therefore not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.